add dstAT param to xform steps

All the existing calls are ported over, and new tests cover
unpremul output. (Opaque output is an impossible request.)

Change-Id: I744d640763cf74c368d3b3aba4a262c8fd9f7a01
Reviewed-on: https://skia-review.googlesource.com/147100
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
diff --git a/src/core/SkColorSpaceXformSteps.h b/src/core/SkColorSpaceXformSteps.h
index 912ae8a..adb92d8 100644
--- a/src/core/SkColorSpaceXformSteps.h
+++ b/src/core/SkColorSpaceXformSteps.h
@@ -31,14 +31,7 @@
     };
 
     SkColorSpaceXformSteps(SkColorSpace* src, SkAlphaType srcAT,
-                           SkColorSpace* dst);
-
-    static SkColorSpaceXformSteps UnpremulToUnpremul(SkColorSpace* src, SkColorSpace* dst) {
-        // The need to transform unpremul to unpremul comes up often enough that it's
-        // nice to centralize it here, especially because this use of kOpaque_SkAlphaType
-        // isn't the most intuitive.  We basically want to always skip unpremul and premul.
-        return SkColorSpaceXformSteps(src, kOpaque_SkAlphaType, dst);
-    }
+                           SkColorSpace* dst, SkAlphaType dstAT);
 
     void apply(float rgba[4]) const;
     void apply(SkRasterPipeline*) const;